Bootstrap drivers are well known in the prior art. In particular metal oxide semiconductor field effect transistor (M0SFET) circuits employ bootstrapping to good effect. Such devices require substantial channel width in order to conduct an appreciable load current such as those commonly used in practice. In general, high capacitance loads require substantial charging currents to improve the speed performance. In the case of lamp drivers, most commonly light emitting diode (LED) arrays, a substantial excitation current is drawn. When such drivers are to be used at low voltage, the problems are aggravated. When MOS devices are operated in the 15-30 volt range, no real drive problems are encountered and conventional circuits can be employed. However, the 9-volt battery has long been an economical power source and at this level MOS driver problems become apparent. At this level bootstrapping is commonly employed.
At the 6-volt level, another common economical power source voltage, driver problems become more acute and bootstrapping becomes very important. At still lower voltages severe problems set in and bootstrapping becomes necessary. In a typical MOSFET enhancement mode device a threshold voltage of about 1.5 volts is common. This is an appreciable fraction of 6 volts. Since, in a conventional driver, the output voltage limits at about one threshold below the supply voltage, the output voltage swing becomes limited. In driver applications substantial areas are involved in obtaining currents in the tens-of-milliamperes range. Bootstrapping will overcome the output swing limit so that the output swing will not be limited by the threshold voltage. Also with bootstrap drive, area consumption can be reduced significantly.